Apparatus for forming circular bushings



April 13, 1937. V J, C, LEMWNG V 2,077,336

` APPARATUS FOR FORMING CIRCULAR BUSHINGS Filed Jan. 7, 1935 3Skleets-Sheet 2 NVENTOR' ..fa/517 Lemmz'gy MJWHQLWLW f :ZLLY

ATTORNEYS April 13, 1937.

J. c. LEMMING 2,077,336

Filed Jan. 7, 1935.

INVENTOR ..z/afin fl Lamra/1117 W His A-noRNEYs Patented Apr. 13, 1937UNITED STATES APPAEATUS FOR. FORMING CIRCULAR BUSHINGS John C. Lemming,Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., acorporation of Delaware Application January 7, 1935, Serial No. 588

Claims.

This invention relates to an apparatus for' forming circular bearingbushings or similar forms from fiat metal stock.

An object of the'invention is to provide an im- 5 proved means formaking bushings having uniformly exact finished dimensions and whichwill have uniformly smooth and efficient interior bearing surfaces.

This application is a continuation-in-part of my copending applicationSerial No. 577,246,

filed November 25, 1931.

In making bushings according to the disclosure of said priorapplication, the opposed ends of the U-form blank directly abut eachother with a high pressure while said U-form blank is being buckledoutwardly into circular form by the approaching semi-cylindrical dies.Such direct abutment of the ends of the U-form sometimes causes one orthe other of the end surfaces of these ends to be scored or grooved ator below the inside surface of the formed bushing. Then when the formedbushing has its inside surface cut away slightly by the usual reaming orother suitable finishing operation, a small axially extending score orgroove will be exposed on the inside or bearing surface of the finishedbushing.

Any such axially extending groove in the bearing surface isobjectionable since it has been found to often be the cause of Vibrationof the shaft running in the bearing, or more rapid wear of the bearing.Such an axial groove in the finished bushings often occurs when thematerial used for the blank is quite soft, such as ordinary bearingbronze stock.

An improvement included in the disclosure of the present application isthe longitudinal inwardly projecting web or key in one of thesemicylindrical dies against which the opposed ends of the U-form abutduring the buckling oper- 40 ation, thus preventing any objectionablescoring or grooving of the end surfaces of the ends of the U-shapedblank. This eliminates the above described a-Xial groove at the seam ofthe finished bearing in all cases whether or not the material 45 of theblank is quite soft.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein a preferred embodi- 50 ment of the present inventionis clearly shown.

In the drawings:

Figs. 1 to 8 are substantially identical `with Figs. 1 to 8 of my saidcopending application Serial No. 577,246.

metal from which the bushing is to be formed.

Fig. 2 shows the fiat strip being sheared off and bent into U -form by areciprocating die.

Fig. 3 shows the U-form in position between two exterior half-dies andan interior floating arbor, just prior to the descent of the upperhalfdie.

Fig. 4 shows what happens during the first portion of the down stroke ofthe Vupper half-die. Here the bottom ends of the U-form have been bentinwardly under the floating arbor and caused said arbor to be raisedsomewhat to permit the ends of the U-form to come together easily; V

Fig. 5 -shows the completion of the down stroke of the upper half-dieshown in Figs. 3 and 4. Here the U-form -has been buckled out intoapproximately circular form'by the dies and the central floating arborhas been forced to its down position and aids in causing the bushing tobuckle out into substantially circular form though this circular form isnot exact.

Fig. 6 shows another station where the bushing is being reformed to amore exact circular form and to slightly smaller inside and outsidediameters which are its final dimensions. The dotted lines indicate theoriginal size before reforming but the reduction in diameter isexaggerated to enable it to be shown. Here the metal of the bushingwalls isV flowed slightly under the high pressure of the exteriorhalf-dies to form the bushing to exact dimensions and give the metal apermanent set.

Fig. 7 is a section on line 'l-l of Fig. 6 and Fig. 5 and shows thesuccessive forming operations of those two figures. p

Fig. 8 is a section on line 8-8 of Fig. 6 and Fig. 5.

Figs. 9 to 1,2'i1lustrate the iniprovements'herein disclosed but notdisclosed in said prior application.

Fig. 9 is similar to Fig. 3 but shows the inwardly projectingabutment'key fixed to the lower halfdie.

Fig. 10 is similar to Fig. 4 and shows whatV forming of the bushing byan interior cylindrical arbor and the final closing of the spaced scamshown in Fig. 11.

Similar reference characters refer to similar parts throughout theseveral views. First there will be described the means and methodillustrated in Figs. 1 to 8.

The flat metal blank ID is preferably sheared off from the end of acontinuous strip 9 of flat stock of bronze or other suitable bearingmetal by the edge 8 of the reciprocating die I2. If

desired, oil grooves, holes and/or trade-marks' may be stamped in theblank I by suitable dies prior to the stroke of the die I2 which shearsoff blank IU. The blank I is then bent into the U-form II by thecontinued down-stroke of the reciprocating die |2 over the stationarycentral die I3. I4 is a stationary stripper bar which aids in guidingthe flat blank l0 into proper position between dies I2 and I 3, andprevents the next following up-stroke of die I2 from dragging the U-formI I up with it, all as will be clearly understood from viewing Fig. 2.

The U-form II next is passed endwise from its position on die I3 to theposition Vshown in Fig. 3

where its lower ends IE rest by gravity upon the curved surface iii ofthe stationary lower halfdie 20, the upper half-diefl2l being at thattime at a higher position than as shown in Fig. 3 to provide properclearance between it and the top of U-form II. An interior floatingarbor 22 is suitably supported in the position shown in Fig. 3 by aprojecting end shank I9 (see Figs. 7 and 8) so that it may be easilymoved vertically upward a small distance by the ends I of the U-form IIas they are forced together as shown in Fig. 4. Floating arbor 22 hascylindrical surfaces 23, 24 and flat'sides to enable it to properlyclear the sides of U-form II which at this time are much closer togetherthan the full inside diameter of the bushing to be formed. Now when theupper half-die 2I descends it compresses the U-form II between dies 2Iand and causes the lower ends I5 of the U-form to rst cam inwardly onthe semi-cylindrical surface of die 20 until they pass under the freelyfloating arbor 22 and raise it upwardly by buckling at the points 25,all as clearly shown in Fig. 4. From this point, further down movementof 'the upper half-die 2| rounds out the U-form II into the nearlycircular form as shown in Fig. 5. During this forming, the cylindricalsurfaces 23 and 24 of arbor 22 aid materially in rounding out the topand bottom portions of the U-form I I and` this causes the flat sides ofthe U-form to always `and uniformly buckle outwardly rather thaninwardly even though said flat sides are spaced some distance from theinterior arbor 22. Another very import'antV function of the floatingarbor 22 is to prevent the formation of a raised internal bead in theformed bushing where the two ends I5 of the U-form II abut at highpressure when die 2I descends as described above. The diameter of thecircular surfaces of arbor 22 is preferably several thousandths of aninch less than the inside diameter of bushing 30, formed as abovedescribed, to permit said formed bushing 30 to be easily slipped endwisefrom arbor 22 after the upper half-die 2I moves up again on itsupstroke. Since arbor 22 is floating, that is, it is not held in fixedposition but may be moved up- Ward freely for a short distance, thepressure of bushing 30 upon the lower half-die 20 is immediatelyreleased when die 2I starts on its up-stroke and henc'e this featurealso permits easy endwise movement of bushing 30 from arbor 22.

For the final forming operation shown in Fig. 6 the bushing 30 isslipped endwise from the flatted arbor 22 onto the slightly smaller butfull cylindrical arbor 42. This cylindrical arbor 42 is mounted upon abolt 43 screwed into the end of fioating arbor 22 and hence arbor 42 isalso fioating (see Figs. 7 and 8). Preferably there is a small clearance44 between the central aperture in arbor 42 and bolt 43 so that arbor 42can move slightly relative to arbor 22, in order that the formingoperation of Fig. 6 will be substantially' independent of that of Fig. 5even though the' exterior half-dies and 4I are formed integral with thehalf-dies 20 and 2I as clearly shown in Figs. '7 and 8. During thisfinal forming operation of'Fig. 6 all small bumps or irregularities inbushing 30' are smoothed out and the walls of said bushing arecompressed under high pressure between the half-dies 40, 4I and thecentral arbor 42 to such an extent that the metal thereof is flowedslightly to cause it to permanently set in its formed exact dimensions.The cold working given the metal by the described reduction in diameterof the bushing at the station shown in Fig. 6 also improves the bearingqualities of bronze metal. At the next up-stroke of upper half-die 4|the finally formed bushing 30' is slipped end- Wise from the end ofarbor 42 by the movement to the left (as seen in Figs. '7 and 8) of thesucceeding bushing 30 as it is moved to its position on arbor 42. Sincearbor 42 is slightly smaller in diameter than the cylindrical portion ofarbor 22, bushing 30 slides easily to its position upon arbor 42. lI'hismovement to the left (as seen in Figs. '7 and 8) of both bushings 30 and30' is done by .automatic means not shown since it forms no essentialpart of this invention.

It is to be understood that the operations described above preferablyare continuous, that is, the U-form II is made at one station, theinitial forming of bushing 30 is done at a second station, and the finalforming of bushing 30' is done at a third station, all at one downstroke of the punch press carrying the dies corresponding to these threestations.

The bushings coming from the third station, that is, from arbor 42 maylater have their ends cut smooth or chamfered in a suitable trimmingmachine if it is so desired, but otherwise these bushings are ready tobe mounted as bearings in the machine in which they are to be used.

The operation of the means shown in Figs. 9 to 12 will now be described.In Figs. 9, 10 and 11' the lower half-die 20' has a longitudinallyextending flat key fixed thereto and extending up into the formingcavity as clearly shown. The fiattened floating arbor 22' has alongitudinal slot 5| therein which fits snugly upon key 50 with an easyslip fit. Thus clearance for key 50 is provided when dies 28' and 2i'close (as shown in Fig. 11) and also key 50 serves as a suitable guidefor the small vertical motion of the floating arbor 22'. Otherwise theparts shown in Figs. 9 to 12 are exactly as described above for Figs. 3to 6.

In operation, the U-form blank I i is first passed to the position shownin Fig. 9 where its lower ends I5 rest by gravity upon the curvedsurface IS of the stationary lower die 22'. The upper die 2I' is shownpartly descended in Fig. 9 until it engages the upper curved end of theU-form I I. Further downward movement of die 2I' now causes vthe ends I5of U-form II to first cam incil.

wardly on the cylindrical surface [6 until they pass under the floatingarbor 22' and raise it upwardly a slight amount by buckling at thepoints 25, as shown in Fig. 10. The end surfaces |5 of U-form ll abutagainst opposed sides of the inwardly projecting flat key 50 (ratherthan against each other as in the form of the invention described above)and are thus prevented from scoring or grooving each other. Furtherdownward movement of die 2l' rounds out the bushing blank into thenearly circular form 60 shown in Fig. 11. During this forming thecylindrical surfaces 23' and 24' of arbor 22' aid materially in roundingout the top and bottom portions of the blank I l and thus cause the flatsides of the U-form to always buckle outwardly rather than inwardly.Also an important function of arbor 22' is to prevent any thickening ofthe ends |5 by a flow of the metal due to the high pressure With whichthey abut the flat key 50 during the forming shown in Fig. 11.

The circular form BU With the spaced seam therein (due to the ends l5being spaced apart by the thickness of key 50) is easily slipped endwisefrom the arbor 22' and onto the circular arbor 42' after the upper die2l' moves up again on its up-stroke in the same manner as describedabove for the bushing 30. The final forming of bushing 60' is done bythe floating circular arbor 42' and the two half-dies 40' and 4l' asshown in Fig. 12, the operation being substantially the same asdescribed above for the final forming of bushing 30' shown in Figs. 6and 8. During this final forming of the bushing the spaced seam 35 shownin the form 60 in Fig. 11 is fully closed by the dies since the flat key50 extends only throughout the length of the forming surface of die 20'.Of course the diameters of the dies 40' and 4I' and of circular arbor42' are sufiiciently smaller than the diameters of dies 20' and 2l' andof arbor 22' to provide for the complete closing of the open seam inbushing 60. Such reduction of diameters of the dies in the final formingstage readily permits the partially formed 45 bushing 60 to be easilyslipped endwise from the arbor 22' to its final forming stage where itsurrounds circular arbor 42'. Floating arbors 22' and 42' are attachedby pin 43' and both move upwardly together a short distance by ayielding 50 spring action to the position shown in Fig. 9 immediatelyupon the up-stroke of the integral upper dies 2l' and 4l'. This floatingaction of the arbors greatly facilitates the endwise movement of bushing60 to its final forming position and also the endwise ejection of thefinal bushing 60' from the end of the circular arbor 42', as describedabove.

While the embodiment of the present invention as herein disclosed,constitutes a preferred 60 form, it is to be understood that other formsity and rigidly fixed to one of said dies and forming an immovableabutment for the opposed edges of said U-form blank during the formingoperation.

2. In an apparatus for making a circular bushing from a U-form metalblank, in combination, two relatively reciprocating dies having coactingsubstantially semi-cylindrical forming cavities which engage andcompress said U-form blank therebetween and force same to buckleoutwardly into substantially cylindrical form, and a thin longitudinalkey fixed to one of said dies and projecting inwardly at the center lineof one of said semi-cylindrical cavities and forming an immovableabutment for the opposed edges of said U-form blank during the formingoperation, and a central arbor located Within said die cavities when inclosed position and having a cutout recess for clearing said inwardlyprojecting key.

3. In an apparatus for making a circular bushing from a U-form metalblank, in combination, two relatively reciprocating dies havingcoacti-ng forming cavities which engage and compress said U-form blanktherebetween and force same to buckle outwardly into substantiallycircular form, and a longitudinal key projecting into the forming diecavity from one of said dies and forming an abutment for the opposededges of said. U- form blank during the forming operation, and afloating arbor positioned between said coacting cavities and having areduced width such that said U-form blank may pass thereabout prior tobeing formed into circular shape, said floating arbor having a slottherein vfor receiving the inner portion of said key projecting beyondthe wall thickness of the formed bushing.

4. In an apparatus for making a circular bushing from a U-form metalblank, in combination, two relatively reciprocating dies having coactingforming cavities which engage and compress said U-form blanktherebetween and force same to buckle outwardly into substantiallycircular form, and a. longitudinal key projecting into the forming diecavity from one of said dies and forming an abutment for the opposededges of said U- form blank during the forming operation, and a floatingarbor located between said coacting dies and movable relative to both ofsaid dies toper- Vmit the opposed ends of said U-form blank to passtherearound while being bent into circular shape, said arbor having aslot therein for receiving the inner portion of said key.

5. In an apparatus for making a circular bushing from a U-form metalblank, in combination, two relatively reciprocating dies having coactingforming cavities which engage and compress said U-form blanktherebetween and force same to buckle outwardly into substantiallycircular form,

JOH'N C. LEMMING.

